JPS59218932A - Method for detecting external damage of cable - Google Patents

Abstract

PURPOSE:To detect easily the external damage of a cable by arranging an airtight tube of which one end is closed in the cable along the longitudinal direction of the cable, and keeping the inner pressure of the airtight tube to a value different from atmospheric pressure, measuring the change of pressure difference between the inner pressure of the airtight tube and the atmospheric pressure by a pressure meter. CONSTITUTION:The cable is obtained by twisting plural cable cores 1 and storing these cable cores 1 in a cable sheath 3 together with the tube 2 enabled to resist neccessary inner pressure. Terminal parts 21 are connected to both ends of the cable 22, and a pressure medium coupling pipe 23, a valve 25 and a pressure meter 24 are connected to the terminal parts 21. One end of the tube 2 is closed and air or the like is injected from the other end with the pressure more than atomospheric pressure, so that the pressure meter 24 can detect the generation of external damage on the cable immediately.

Description

[Detailed description of the invention] TECHNICAL FIELD This invention relates to detecting trauma to electrical cables.

Cables are generally laid along long routes, often with other structures, and are typically buried, so it is generally relatively difficult to inspect their condition after installation. Therefore, if the cable is damaged during use, it may be flooded or corroded by metals such as the conductor, metal tape for shielding, metal wire, metal tape for shielding, etc., and there is a possibility that the cable will lose its performance or function as a couple. be. In addition, immediately after receiving an injury, it is difficult to detect damage to the cable, such as water ingress, which can be confined to the vicinity of the injury, and thus it is difficult to prevent the damage from spreading along the cable.

It is an object of the present invention to overcome the above-mentioned difficulties in detecting damage to conventional cables.

According to the invention, an airtight tube with one end closed is disposed inside an electric cable having a conductor, an insulator, and a sheath, the pressure inside the tube is maintained at a pressure different from atmospheric pressure, and the pressure inside the tube is maintained at a pressure different from atmospheric pressure. The above objective is achieved by providing a pressure gauge to detect changes in the difference between the tube internal pressure and atmospheric pressure.

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of a cable particularly suitable for carrying out the method of the invention. In FIG. 1a, a plurality of cable cores 1 made of conductors and insulators are twisted together, and an appropriate gap between the cable cores 1 is made airtight.
A tube 2 that can withstand the necessary internal pressure and is continuous in the longitudinal direction of the cable is placed vertically or, for example, twisted with the same pinch as the core twisting pinch, and the cable north 3 is provided on top of it. Thus, the cable of the present invention is constructed. FIG. 2 shows an example of a modification in which opening a plurality of tubes 2 increases the probability of detecting external injuries.

After the cables are installed, one end of these tubes 2 is closed, and a suitable gas, such as air or a non-contaminating liquid, is filled from the other end at a pressure above atmospheric pressure. FIG. 6 is a schematic diagram showing an example of the configuration of a device for detecting damage to such a cable. That is, such a cable 22 is provided with terminal portions 21 at both ends, and a ξ-ib 23 and a valve 25 for connecting the pressure medium are connected to each terminal portion.
For example, one end of the tube 2 within the cable 22 may be closed by the valve 25 on the left side of FIG.

A pressure gauge 24 is provided on the left side ξ Eve 23,
To constantly monitor the pressure of a pressure medium in a tube 2. With this configuration, the cable 22
If the pressure medium leaks due to trauma, this can be immediately detected using the pressure gauge.

In this way, when S-lubes are used at both ends, it is extremely advantageous to apply pressure to the pipe from both ends after the trauma detector and measure the pressure-flow rate to estimate the external pressure.

Figures 3 to 5'/'i show other embodiments of the present invention. In FIG. 3, a tube 2 having a circular cross section is arranged between a single-core cable consisting of an insulator 12 and a conductor 13 and its sheath 14, and this tube 2 is made of a hard material. FIG. 4 shows a similar arrangement of flat tubes 2' as tubes, which is effective in preventing an increase in the outer diameter of the cable. The trench shown in FIG. 5 increases the width of the flat tube 2'' of FIG. 4 to increase the coverage of the cable core, thereby achieving the same effect as in FIG. 2.

In the above, we explained how to detect external pressure by applying pressure inside the tube and taking advantage of the fact that the pressure decreases when the tube breaks due to external trauma. It is also possible to maintain the inside of the tube in a reduced pressure state and detect trauma 4o by an increase in the internal pressure of the tube. Furthermore, although an example has been described in which the trauma detection tube is placed between the sheath and the wire core, it is also possible to embed it in the sheath itself.

As described above, according to the cable of the present invention, if the sheath is damaged due to trauma after installation and the trauma detection tube is damaged, the pressure inside the tube changes with respect to atmospheric pressure, but this can be monitored with a pressure gauge. This allows the fact to be detected immediately and recovery measures to be taken, thereby making it possible to repair or restore damage to the cable itself or its lines, even if the damage is minor.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of a cable for carrying out the method of the present invention, FIGS. 2, 3, 84 and 5 are sectional views of other embodiments, and FIG. FIG. 3 is a diagram illustrating the present invention in detail. 1... Wire core, 2, 2', 2'' - Trauma detection tube, 3... Sheath, 21... Cable end, 22
・Cable, 23...For pressure medium connection ・ξ Eve, 24
...Pressure gauge, 25...Valve.

Claims (1)

[Claims] (1) An airtight tube with one end closed is installed vertically inside the cable to maintain the pressure inside this airtight tube at a value different from atmospheric pressure, and a pressure gauge is installed at the other end to keep track of the airtight tube internal pressure and atmospheric pressure. A method for detecting damage to a cable comprising monitoring changes in the difference between the cable and the cable.